1,3-butylene glycol is conventionally manufactured by alcohol condensation of acetaldehyde to yield acetaldol which is then hydrogenated to 1,3-butylene glycol as described in WO 2005/068408. There are various processes recognized for producing 1,3-butylene glycol commercially. U.S. Pat. No. 6,376,725 discloses a process for producing 1,3-butylene gycol through a liquid phase hydrogenation of acetaldol (3-hydroxybutanal or aldol) in the presence of a Raney nickel catalyst. Acetaldol is commonly produced through the aldol condensation of two molecules of acetaldehyde. U.S. Pat. Nos. 5,345,004 and 5,583,270 disclose producing 1,3-butylene glycol in three-step processes including an aldol condensation of acetataldehyde to aldoxane, followed by decomposition of the aldoxane to obtain paraldol which is in turn hydrogenated to produce 1,3-butylene gycol.
Because the odor and odor stability over time is an important aspect of the product, various methods to remove odor causing impurities have been suggested in the art.
U.S. Pat. No. 6,900,360 to Tsuji et al. describes methods of preparing purified 1,3-butylene glycol from acetaldehyde. Acetaldehyde is condensed and the acetaldols are then converted to 1,3 butylene glycol. Chemical treatment with alkaline or acidic reagents or with ozone is used along with distillation to provide purified product.
U.S. Pat. No. 6,376,725 also to Tsuji et al. discloses 1,3-butylene glycol obtained from acetaldol by a liquid phase hydrogen reduction method, by adding a base to crude 1,3-butylene glycol free of high-boiling material, heat-treating the mixture and then distilling off 1,3-butylene glycol; and distilling off low-boiling materials from 1,3-butylene glycol.
A very similar process is described in JP 7258129 wherein a process to distill and purify 1,3-butylene glycol from a reaction mixture obtained by liquid phase reduction of acetaldol with hydrogen, at least one compound selected from sodium hydroxide, potassium hydroxide, sodium borohydride and potassium borohydride is added to the process to remove the high-boiling impurities contained in the original crude 1,3-butylene glycol.
United States Patent Application Publication No. US 2004/0254407 teaches to extract impurities from 1,3-butylene glycol by mixing the glycol with water and an organic solvent and to recover 1,3-butylene glycol from the aqueous phase by distillation or dehydration.
JP 61-065834 teaches to remove impurities from 1,3-butylene glycol by carrying out continuous distillation of 1,3-butylene glycol under reduced pressure with a thin-film evaporator while adding water to the system.
JP 2003252811 teaches to treat 1,3-butylene glycol with a non-ionic porous resin of styrene and divinyl benzene to remove impurities.
While various methods have been proposed to purify 1,3-butylene glycol, it is seen from the foregoing references that such processes are either complex or require specialized and expensive materials as is a process for purifying diglycerol (apparently to remove acroleins) by treatment with activated carbon followed by distillation described in JP 04217637.
In accordance with the present invention, 1,3-butylene glycol with reduced or no odor is obtained by treating conventionally produced 1,3-butylene glycol with certain activated carbons.
Activated carbons are readily available and may be purchased in the form of powders, granules or extruded pellets. Activated carbon is microcrystalline, non-graphitic form of carbon which has been processed to develop internal porosity. Almost any carbonaceous material of animal, plant or mineral origin can be converted to activated carbon if properly treated. Coal, hardwood or softwood sawdust or coconut shells, for example, can be used as the starting material. Activated carbons are further characterized by surface area, density and method of activation. Compounds used to chemically activate carbon are alkali metal hydroxides, carbonates, sulfides, sulfates; alkaline earth carbonates, chlorides, sulfates and phosphates; zinc chloride; sulfuric acid and phosphoric acid.
Alternatively, carbon may be activated by selective oxidation by treatment with steam, carbon dioxide or flue gas. Further details are described in Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Ed., Vol. 4, pp. 561-569, the disclosure of which is incorporated herein by reference.